Cut steak in half lengthwise, then holding knife almost parallel to cutting board, slice steak crosswise into 1/8 inch thick slices; place steak in a bowl with soy sauce.
Remove peel and white pith from 2 oranges with a sharp paring knife, slice into 1/4 inch thick slices, then cut each slice in half.
Using the last orange, grate 1 teaspoon of peel and squeeze 1/2 cup of juice.
In a large nonstick pan, melt 2 teaspoons margarine over medium high heat, add both peppers and sauté until tender crisp, place in a large bowl.
Return pan to heat and melt 1 teaspoon of margarine, add green onion and sauté until tender crisp, place in bowl with peppers.
In a separate small bowl, mix the orange peel, orange juice, ginger, and cornstarch until well mixed, set aside.
Return pan to heat again and melt remaining 1 tablespoon of margarine, add half the beef mixture, stir quickly and continuously until beef is no longer pink, place in bowl with vegetables using a slotted spoon.
Cook remaining beef in the drippings in pan.
When cooked, return all of the cooked beef and vegetables to the pan; add orange juice mixture and sliced oranges.